02 emissions

[peter306]

Probably not a new topic but my car has just failed the MOT. 02 emissions too high, everything else good

Fast idle was 1.10% max .30%

Second fast idle was 0.59% max .30%

Natural idle test 0.48% max .50%

just 02 emissions, everything els was a pass

[RichardW]

Presumably that should be CO emissions? I would expect the lambda to be off as well, but it may have just scraped in. Sounds like a new cat is in order to me - but a good hard thrash to the MOT station and retesting with it good and hot might get it through.

[qprdude]

Peter, knowing what car/engine you're talking about might get some advice on the likely cause.

[peter306]

Richard, yes your right, glitch on my brain.

W reg Xantia 1.8 petrol 16 valve

fast idle test
engine speed 2606 rpm pass
CO Max allowed 30% reading 1.10% Fail
HC Max 200ppm reading 93ppm pass
Lambda 9.97-1.03 reading 1.03 pass

Second fast idle test
Engine speed 2898 rpm pass
CO max 0.30% reading 0.59% fail
HC max 200ppm reading 39ppm pass
Lambda 0.97-1.03 reading 1.02 pass

Natural idle test
Engine speed 700-1000 rpm reading 937 rpm pass
CO max 0.50% reading 0.48% pass

[RichardW]

Ir's not far off... put some decent petrol in it, and possibly some cat clean snake oil, then take if a damn good thrash - high revs and work it hard. See if you can arrange to take it just to get it put on the analyser - and take it really hot, it might well pass.

[peter306]

Yes it is close, it was fluctuating up and down on the testers analyser, first test kept going between about .80% ant the 1.10%, second test got down to around .45%
I was in Burton on Trent at the weekend, it did 130 miles mostly motorway on the way back to just south of Swindon, Petrol station fuel. going to check the Air Filter and plugs as i didn't have time when i got back home.
Don't know if this has any relevance but I had to change both Dip Beam bulbs (thats why i was late back), once i had that done i checked them and forgot to turn them off and flattened the battery,even the remote key wasn't having any, had to put it on charge,

[RichardW]

Ah, if it's wandering about, then could point to a lambda sensor problem. Check on the lexia what the signal is doing, it should go from low to high volts about once a second when warmed up.

[peter306]

Hello, hopefully Taffy is still around and available in Swindon

[peter306]

Looks like you are right Richardw, got it on a diagnostics scanner yesterday, microvolts all over the place, waiting for a new Lambda sensor now then put it in for retest

[Mandrake]

Is there any sort of misfire or loss of power ?

High HC and CO readings generally mean either it's running rich or it's misfiring. (incomplete combustion of fuel)

As a lamba reading of 1.03 is on the lean side I'd be looking more towards a misfire.

When was the last time the spark plugs and/or spark plug wires (if it has any) were replaced ?

[peter306]

Hello Mandrake,
No misfire or loss of power, plugs and air filter changed in the last week.
No problem with HC readings, only the CO and only on fast idle, the CO reading was fluctuating rapidly on the testers analyser.
Had it diagnosed yesterday at Pryton Engineering, Len is a Citroen specialist, He put it on his scanner and the lambda sensor voltages were jumping all over, got a new one coming so have to see, the old one was a cheapy of Ebay.

[Mandrake]

If it's a cheapy ebay O2 sensor definitely get that replaced with the genuine article first and then see if there is still a problem.

"Universal" O2 sensors are false economy - they seldom work quite right as their specs don't match the original. Been there done that!

[peter306]

Well, it went for it's retest this afternoon after new plugs, filters and lambda sensor, and we have a pass.
First fast idle CO 0.38%
The computer said further conditioning needed
Second fast idle CO 0.09%
Weird thing, on the second fast idle it was hovering around 31-33% then suddenly shot down to 0.09%
Natural idle down to 23% CO
MOT guy thinks the broken lambda sensor may have slightly damaged the cat.